Lioyd espenscjiied



Fatented Feb. 27,

UNITED sures res-sea PATENT orFic L'LoYD Esrnnscnrnn, or nonms,,nntv,YonK, essrsnen TO AMERICAN TELEPHONE AND TELEGRAPH cor/inertia, a CORPORATION on NEW RK; t

name nnonrvms nrrnnnirns. v

Application filed. June .7, 1918. Serial No. 238 723.

To all whom it may c0nceriz-.'

Be it known that I, Lnoyn Esennsoninn, residing at'Hollis, Long Island, in the county of Queens and State of New York, have invented certain Improvements in Radio Receiving A.1 )1;iaratus,'of which the following 18 a specification. 1 I

This invention relates generally. to systems for transmitting energ and particularly'to the protection of such systems againstidisturbance. Tts object is to provide a method of and apparatusfor elii'ninating or minimizing the effects of disturbancesin such systenis,whether in power circuits or signalling systems, and in either wireor wireless systems of communication. The invention finds one very important application in the radio transmission of intelligence as a. protection against the electrical disturbances commonly known as static andthe invention will be here described as applied to'such a system, but, as will clearly appear hereinafter, the invention is of much broader applicability.

Inradio signalling systems the usual antenna is sharply tuned to increase its responsiveness to waves of the particular frequency to be receivedand to. reduce the liability of interference from signals; of other frequen cies. The effect of static disturbances upon. an antenna thus sharply tuned seems to be analogous to that ofablow upon a tuning fork, that 18 the energy of the impact lsconverted largely into oscillations of the frequency to which the device is tuned' In a wireless receiving system thismeans that the disturbance will appear in the receiver to the confusion of the signals it is desired to ob serve. In other words the receivingsystems, instead of-excluding the static disturb ances by reason of existing differences be tween them and the signaling: impulses, or instead of accentuating or producing differences between them tends to effectually eX- tinguish the differences that 'do exist. so that the disturbance is in a sense manufactured by the system for its own receiver. Like phenomena may occur inalmost any energy transmission system where some or all of the transmitting mediunihas a natural period or is capable of responding sympathetically to foreign disturbances.

This invention proposes to avoid such dis? turbance by changingordiverting the disturbing energ intoaplurality of freemancies othenthan that of theenergy to be transmitted or into a band of frequencies of considerable extent so that, even though the frequency being transmittedfalls within its scope, only a small proportion of the dis turbance reaches the translatingor indicating: devicesof '"h system. I

QThe inventioirwill be more fully understood by reference to the following description and the accompanying drawing in which: i 1 Figure 1 is a .diagrainmaticillustration of the receiving end'of a radio signaling system embodying the invention and in which a wave filter form of antenna is employed.

Fig. 2 is a modification in which a wave filter circuit is associated with an aperiodic antenna. i I

Fig. 3 is a varianto'l' the arrangement shown in Fig. 1.

iig. 1 is a curve indicatii'ig generally the operation of the system. i

Thecombination of a filter type of antenna with the receiving circuit and the filter type of antenna per se, as shown in Figures 1 and 3, are separately disclosed a nd claimed in my copending application, Serial No. 613,226, filed January 17,1923.

In Fig. 1, 10 represents the antenna of the receiving); circuit arranged in the form of' wave filter, consisting of a horizontalconductor 11 grounded at intervals, as shown, by vertical conductors 12. Impedance, here shown as -capacities 13 and inductance/s 14, is located in each'section of the'horizontal conductor. that is, between each two ground I ed conductors. Eachgroundedconductor is,

also provided with impedance, shown in this instance asa capacity 15 and an inductance 16. arranged in parallel.

I The wave filter per se is theinvention of G. A. Campbell, an'dgas disclosed in his Patent 1,227,113, May 22, 1917, may assume any" one of several forms. Thus. for the purposes of tuning" to respond to different from any set of iuductauces or camow g'iacities above indicated, may be omitted, or their values adjusted;

Between this and the antenna is placed a device 18 for the purpose of preventing reaction between the sharply tuned circuit 17 and the filter circuit. In the present instance, this is illustrated as an audion having the usual filament, grid and plate, and the batteries A, B and C for controlling its action. hen the audion is used for this pur pose, it is adjusted to amplify to a large degreein transmitting energy from the filter circuit to the tuned circuit 17 in which case its effect when transmitting in the opposite direction is negligible. This prevents the circuit 17 from becoming in effect one section of the antenna circuit and partaking in forming the natural oscillations of various frequencies present in that circuit. The device 18 may conveniently be called a one-way device by reason of the characteristic just pointed out. It is possible to omit it entirely if the coupling between the tuned circuit 17 and the antenna is made sufficient ly loose to prevent the undesired reaction mentioned.

The device 18 is connected to the antenna circuit by conductors 19, which are here shown as terminating at the end vertical conductor, though it will be understood that this connection may be otherwise located. Transformers 2-0 and 21 are interposed, as usual, in the circuit at either side of the one-way device to localize the battery currents and to give any desired ratio of transformation.

22 is a detector for the signaling current, here shown as of the audion type and operating in a well known manner. It is coupled with the receiver 23 by transformer 24 in the usual way.

In the modification illustrated in 2, the antenna 25 is preferably designed to be aperiodic. To this end the noninductive resistances 26 are distributed throughout its length. one end to the antenna, in the present instance, across the terminals of a non-inductive resistance 28. The filter circuit is here illustrated as having the capacities and inductances 13 and 14 in the horizontal condnctor, and the capacities .15 in the vertical conductors, but omitting the inductances 16 shown. in Fig. '1. Inasmuch as the filter circuit is not used as the antenna in this instance, a lower horizontal conductor 29 is provided for connecting the lower ends of the conductors 12. As above suggested, the omission of the inductances 16 in this modification merely results in giving the filter a different set of natural frequencies. In this modification the one-way device, the tuned A filter circuit 27 is connected at.

zontal component 31 in each of whiclrare located inductances and capacities 352 and 33 in much the same manner as in the horizontal conductor of the modification shown in Fig. 1. As is well known, an antenna, especially one with a horizontal component, as illustrated in this figure, has a natural capacity to ground which may be regarded as distributed along the antenna something after the fashion of the capacities 15 in Fig. 2. The antenna here shown will, therefore, when properly tuned and coupled with the other elements of the receiving circuit above described, operate as a wave filter having a plurality of natural frequencies. Here, as in Fig. 2, the one-Way device, the tuned circuit, the detector and the receiver, correspond to those described in connection with F ig. 1.

Figure t is a curve illustrating the operation of the receiving circuit, in which the ordinates represent current and the abscissa. frequency. The line :0 indicates the band of frequencies to which the filter circuit will respond for sustained or forced alternating current. Lines y indicate the natural frequency periods to which the filter circuit is adjusted. Four such frequencies are indicated in this instance corresponding to the four natural periods of the four section filter circuit shown. In general, for the simple form of wave filter circuit shown in Fig. 2, and also in the form of antenna in Fig. 3, the number of natural periods corresponds to the number of sections of the filter circuit. For the more general form of filter circuit in which both the series and the shunt branches contain both inductance and capacity, as'in Fig. 1, each section exhibits two degreesof freedom, the number of natural periods being then twice the number of sections. The curve 2 indicates the resonance characteristic ofthe sharply tuned circuit 17. The frequencies to which this circuit will respond are located, it will be observed, in a very narrow band between the natural frequencies of the filter circuit. It will be understood that this circuit might be tuned to a frequency lying beyond the natural frequencies of the filter circuit in either direction if the responsiveness of the filter to forced alternating current impulses were made sufficiently broad to allow of such an adjustment The operat on of the receiving circuit will now be readi understood. Static disturb fallinglupon the filter circuitare a gely converted into oscillations of a plnrality of definite frequencies, or bands of frequencies of limited extent, which cor.- respond to the natural frequencies of the circuit. These oscillations, being relatively persistent and for the most part at least, different from the signaling frequency, ar f discriminated against by the sharply Saree tive circuit 17. The signaling impulses are of a frequency dilfering'ffrom thenatural frequencies of the circuit and are received through the filter circuitv by reason 10f its responsiveness to forced alternating cure rent inipulses,as indicated by thecurve m in Fig. 4:.

detector 22, and thus to the receiver, in the usual manner. Inasmuch as the static disnatural frequencies thereof are each repre sented' by a band of more or less extent, it is possible that these may, in some cases, lap over the" signaling frequency. If the bands were conceived as extending toward each other untilthey merge this would be true in all cases, but evenunder these cond-itions the energyof the static disturbance is spread out, so to speak, over a large number of frequencies, whlle the signalmg' frequency is sharply limited, and the resulting would be 131 0% disturbance in the receiver portio-nately reduced;

Since this method of differentiationv is based upon the differencewhieh exists between the disturbance and the signaling current as regards persistency, 'it is obviously desirable'that this difference be preserved to the point at which the currents enter the frequencyconcentrating filter. This desirable condition is fulfilled in the organization of Fig. 1, by incorporating the filter action in the antenna itself so that immediately upon the transference of the energy of the free electric waves into current form, the filter action becomes effective. This is likewise the case in the system of Fig. 3. In the arrangement of Fig. 2, a non-filter antenna is employed to con vey the received energy to the filter circuit. This antenna, 25, is made an aperiodic or non-oscillatory antenna in orderthat the inherent difference as regards persistency between the signals and disturbances may be preserved until the currents enter the filter. An ordinary oscillatory antenna may be employed, however, without departing from the method involved, but it is desirable to couple it closely with the filter circut so that it becomes essentially a part of the filter circuit itself and partakes in. its frequency forming action. To the extent that the antenna is of the oscillatory type and the coupling between it and the filter circuit is These pass through the one-way device l8[w'hich, inthis case, also ample fies them, into the tuned ci1cuit17 to the away from this frequency. It follows, therefore, that in employingthe ordinary type'of' resonant circuit antenna it should be coupled with the filter circuit sufficiently close to become. an integral part thereof with respect to natural oscillations.

It will now be evident that the broad 'method herein employed for differentiating between impulses and steady state forces, orbetween oscillations of different degrees of persistency, is a general method and is not limited to theapplication herein described in detail, but is applicable irrespective of thetype of transmission system (i. e. whether using natural media or wires) or of the form of the energy involved, whether electricalor mechanical, or of the absolute values of the frequencies concerned. In the sphere of wireless transmission, for instance, the method is not limited to electric wave transmission which is usually conducted at ultra-audible frequencies, but may be invoked as well in audible sound-wave transmission, as in submarine signaling.

In this latter art the transmission waves of compression and rarefaction are generated by forces applied mechanically to the water. Inthe case of'ordinary submarine signaling, continuously generated sound waves producing in the receiver a musicalnote are usually employed; and these waves are generated at the transmitter by the rhythmic motion of a diaphragm in the water. Detection of vessels by underwater sound transmission may be accomplished by reason of the waves which are set up in the water by the propelling machinery of the vessel, the driving engines or motors, or the propellers themselves. The receiving of such submarine signals as these is however frequently interfered with by the presence in the water of extraneous pressure waves, caused by surface waves, etc., which act upon the receiving diaphragm and attendant receiving circuits in much the same way as does static 110 upon a radio receiving system, and this may be eliminated by the invention here described.

It will be understood that the method described may also be used in the art of wire 115 electric transmission systems of all kinds. While free transmission systems such as radio and submarine signaling systems are peculiarly subject to the interference of transient disturbances, confined transmission 2 systems such as employ wire circuits are nevertheless not entirely free from this difficulty. Such disturbances may arise in wire systems from external sources, such as lightning or foreign electric systems, or may 1% arise from sources within the wire system itself as from alterations in the energy transmitted. In the caseof power supply circuits, these alterations may be caused by sudden changes of switching, circuit-break- 1S0 er operation, etc, while in signaling circuits they may he even those characteristic. of the signaling itself. lilaniiestly the method and means; described herein are applicable "to the protection of wire systems a ainst such disturbances.

b a v What is claimed is; 1. in a radio signaling system comprising an antenna circuit. a filter circuit connected tion and that of converting static impulses toperiodic oscillations, anddetecting the selected oscillations.

In a radio signaling system comprisingan antenna circuit, a filter circuit connected therewith, a selective circuit connected wlth said filter circuit by a oneway conducting device, and a receiving device connected with said selective circuit, the method of staticreduction which consists in receiving both static impulses and signaling oscillations, converting the energy of the static impulses into a plurality of oscillations differing for the most part in frequency from that of the signaling oscillations, suppressing the oscillations of frequencies other than the signalinaaseo ing frequency, selecting the signaling :lrequency, and preventing undesirable reaction between the selected oscillations and those resulting from the conversion of the static impulses.

3. In a receiving apparatus for signaling systems a circuit having a number of natural periods of oscillation and also being responsive to sustained periodic impulses over a considerable range of frequencies, a sharply tuned circuit, means connecting said circuits for transferring energy from the first named circuit to said sharply tuned circuit and preventing the passage ofenergy in the opposite direction, and signal indicating mechanism associated with said sharply tuned circuit.

4;. In a receiving apparatus for signaling systems, an antenna capable of receiving and transmitting oscillations of varying frequencies and decrements, a filter circuit connected thereto for converting non-persistent impulses into oscillations of a plurality of frequencies, an oscillating circuit sharply tuned to the frequency of the signaling circuit, a coupling uniting the filter circuit and the oscillating circuit, whereby the latter may be excited by the former, means included in said coupling for preventing transfer of energy toward the filter circuit and signal indicating means connected to y the oscillatory circuit.

In testimony whereof, I have signed my name to this specification this twenty ninth day of May, 1918.

LLOYD A SPENSCHIED. 

